Rectifier.



G. S. MEIKLE.

RECTIFIER.

APPLICATION FILED MAY7,1915.

1 1 82,29 1 Patented May 9, 1916.

Inventor His a c torneg.

UNITED STATES PATENT oEEIo GEORGE S. MEIKLE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORA TION OF NEW YORK.

RECTIFIER.

Application filed May 7, 1915: Serial No. 26,606.

To all whom it may concern Be it known that I, GEORGE S. MEIKLE, a citizen of the United States, residing at Schnectady, county of Schnectady, State of New York, have invented certain new and useful Improvements in' Rectifiers, of which ,the following is a specification.

The present invention relates to rectifiers for alternating currents, and its object is to provide a simple and durable device which is self-starting and reliable in operation, and which requires a minimum of auxiliary apparatus.

In accordance with my present invention the rectifier comprises a refractory cathode,

, such as a tungsten filament, adapted to be heated to incandescence so as to emit electrons and a self-reconstructing anode of volatilizable material such as mercury. Although the atmosphere surrounding the heated cathode during operation may consist entirely of mercury vapor derived from the anode, the space within the envelop be ing otherwise deprived of gas, ll may also to advantage provide in the sealed envelop a certain amount of gas other than mercury vapor,for example, a low pressure of argon, nitrogen, or other inert gas.

In the accompanying drawings Figure 1 shows in perspective one embodiment of my invention, and Figs. 2 and 3 illustrate diagramatically systems of connections suitable for using the device to rectify alternating current Referring to Fig. 1, the device consists of a sealed envelop 1 consisting of glass, or quartz. The cathode 2 consists of material which may be heated to a temperature of at least about 2000 (3., such, for example, as drawn tungsten. The cathode is connected to current supply wires 3, 4 sealed into a stem 5 in the usual manner. The terminals of these wires may be joined as illustrated to a threaded base 6. The cathode preferably consists of heavy wire, for example, ten to twenty mils in diameter, closely coiled to form a helix.

The anode 7consists of mercury or amalgain, or other suitable easily volatizable metal and is provided with a sealed-in current supply conductor 8. The cathode and the anode preferably are located close together, as indicated, the distance depending on the potentials to be used in operating the device. The space within the envelop may Specification of Letters Patent.

Patented May 9, 1916.

' electrical disintegration of the cathode takes place too rapidly to give the device a length of life great enough for commercial purposes and at higher pressures the voltage drop is greater so that the efficiency is lower. At this or higher pressure the discharge has the characteristics of an ordinary arc and in appearance resembles an are being hot and contracted to a narrow zone.

In the system of connection shown in Fl g. 2, the cathode and the anode of device D are connected by conductors 8, 9 to the terminals of a source of alternating current, such, for example, as the secondary winding 10 of a transformer T. The terminals of the oathode 2 are connected to another secondary winding 11 of low voltage, the ratio of transformation being chosen to furnish a current suitable to heat the cathode 2 to bright incandescence above about 2000 C. so as to give off a good supply of electrons to ionize the gas or vapor and make it conducting. In series with the conductor 9 is shown a direct current load device, namely, a battery 12 connected in series with a resistance 13. With the switches 14 and 15 closed, the rectification of current starts automatically. Alternate impulses of the alternating current which are negative with respect to the cathode are conducted by the device andthe opposite impulses are entirely suppressed, contrary to the assumption which might be made that the mercury would readily become a cathode. The electric discharge by impact on the anode as well as radiant heat from the cathode quickly vaporizes some of the liquid anode material into the arcing space and the vapor reduces disintegration of the cathode to such an extent that the device has a life approximating a thousand hours. The vaporcondenses on the walls of the bulb and returns to the anode thus constituting the entire surface of the device a mediate connection of the reactance coils by a conductor 22. Half waves of current are transmitted alternately by each discharge device, thus supplying a pulsating direct current to the load which may be smoothed out to a desired extent. by the reactance coil.

If desired he cathode heating current may be cut off after the discharge is normally I operating, the cathode being suficiently heated by the discharge to keep the device in operation. However, I prefer to maintain the heating current and to heat the cathode to a somewhat higher temperature than necessary to furnish electrons sufiicient to trans- I mit the energy, as I find that thelength of life of the cathode is thereby greater than when the cathode is heated only by bombardment of positive ions, the heating current being cut ofi. Since the anode is selfvreconstructing, the life of the rectifier is limited only by the disintegration of the cathode, and it is for this reason that a fairly large filament, such as is now used in the larger incandescent lamps is desirable for the cathode. Of course if this wire is unnecessarily large, a higher exciting current is needed and the efficiency is lowered. I therefore prefer, as I have said, to use tungsten wire of about ten to twenty mils diameter.

the cathode.

What I claim as new and desire to secure by Letters Patent of the, United States, is

. 1. The combination of an envelop, a cathode of material having a melting. point above 2000" (3., a self-reconstructin anode of vaporizable material, means for eating said refractory cathode to incandescence, a

source of alternating current, and connections between said electrodes and said source, the energy supplied by said source being high enough to produce in said envelop a pressure of vapor at which the electrical .dlscharge has the electrical characteristics of an arc.

2. A rectifying device comprising the combination of an envelop, a mercury anode, a tungsten cathode, means for electrically heating said cathode, and a highly attenuated atmosphere of. inert gas in said envelop, the pressureofmercury vapor in said device during operation beinghighenough to give the discharge the characteristidofan arc and suppress electrical disintegration of 3. A rectifier comprising the combination of an envelop, a mercury anode, a cathode of highly refractory metal, and electrical connections for heating said cathode, the Va or pressure in said device during operation eing equal to at least several centimeters of mercury.

4. A rectifier comprising the combination of a sealed envelop, a mercury anode, a cathode of highly refractory material, and electrical connections for independently heating said cathode, the vapor pressure in said device during operation being high enough to cause the electrical discharge to have the characteristics of an arc and to suppress electrical disintegration of the cathode. In witness whereof, I have hereunto set my hand this 6th day of May, 1915.

GEORGE S. MEIKLE. 

